Accessing the Parent's Variables

Just as with sandbox variable access, a sandbox parent's
variables may be read from and written to as properties of
the Runkit_Sandbox_Parent class.
Read access to parental variables may be enabled with
the parent_read setting (in addition
to the base parent_access setting).
Write access, in turn, is enabled through the
parent_write setting.

Unlike sandbox child variable access, the variable scope
is not limited to globals only. By setting the
parent_scope setting to an appropriate
integer value, other scopes in the active call stack may
be inspected instead. A value of 0 (Default) will direct
variable access at the global scope. 1 will point variable
access at whatever variable scope was active at the time the
current block of sandbox code was executed. Higher values
progress back through the functions that called the functions
that led to the sandbox executing code that tried to access
its own parent's variables.

Calling the Parent's Functions

Just as with sandbox access, a sandbox may access its parents
functions providing that the proper settings have been enabled.
Enabling parent_call will allow the sandbox
to call all functions available to the parent scope. Language
constructs are each controlled by their own setting:
print and echo are
enabled with parent_echo.
die() and exit() are
enabled with parent_die.
eval() is enabled with parent_eval
while include, include_once,
require, and require_once
are enabled through parent_include.